Process for the preparation of substituted pyrano (3,2-c) (1,2)benzothiazine 6,6-dioxides

ABSTRACT

wherein R represents hydrogen and lower alkyl; R&#39;&#39; represents lower alkyl and formyl; by reacting, as the first step, the corresponding 2-substituted-2H-1,2-benzothiazin-4(3H)-one 1,1dioxide (II) with a boron trifluoride compound and an acid anhydride IV; alternately, the starting material may be a 3acetyl-2-substituted-2H-1,2-benzothiazin-4-(3H)-one 1,1-dioxide (III) which is reacted with the boron trifluoride compound, without the necessity for the acid anhydride (IV). Starting materials II and III subjected to step one of the process yield novel boron complex intermediates V (2,2-difluoro-4,5disubstituted-2H-1,3,2-dioxaborino(5,4-c)-1,2-benzothiazine 6,6dioxide). Boron complex intermediate V, in the second step of the process, is subjected to treatment with a Vilsmeier reagent (phosphorus oxychloride together with dimethylformamide), followed by hydrolysis. The substituted-pyrano(3,2-c) (1,2)benzothiazine 6,6-dioxides of formula I prepared by the process of this invention have anti-secretory activity and are useful in the treatment of hyperacidity; certain of these compounds demonstrates anti-allergy activity. Process for the production of substituted pyrano(3,2-c) (1,2)benzothiazine 6,6-dioxides and novel intermediates produced thereby of the general formula I:

United States Patent [1 1 Kaminsky Aug. 5, 1975 PROCESS FOR THE PREPARATION OF SUBSTITUTED PYRANO (3,2-C)

( 1,2 )BENZOTHIAZINE 6,6-DIOXIDES [75] Inventor: Daniel Kaminsky, Parsippany, NJ.

[73] Assignee: Warner-Lambert Company, Morris Plains, NJ.

[22'] Filed: May 29, 1973 [21] Appl. No.: 365,398

[52] U.S. Cl. 260/243 R; 424/246 Primary E.\'aminerJohn M. Ford Attorney, Agent, or FirmAlbert H. Graddis; Frank S. Chow; Anne M. Kelly [57] ABSTRACT Process for the production of substituted pyrano[3,2- c] [l,2]benzothiazine 6,6-dioxides and novel intermediates produced thereby of the general formula I:

N-R SO wherein R represents hydrogen and lower alkyl; R represents lower alkyl and formyl; by reacting, as the first step, the corresponding 2-substituted-2H-l,2-benzothiazin-4(3H)-one 1,1-dioxide (ll) with a boron trifluoride compound and an acid anhydride lV; alternately, the starting material may be a 3-acetyl-2- substituted-2H- l ,2-benzothiazin-4- 3H ]-one 1 ,1- dioxide (III) which is reacted with the boron trifluoride compound, without the necessity for the acid anhydride (IV). Starting materials ll and Ill subjected to step one of the process yield novel boron complex intermediates V (2,2-difluoro-4,5-disubstituted-2l-ll,3,2-dioxaborino[5,4-c l ,2-benzothiazine 6,6- dioxide). Boron complex intermediate V, in the second step of the process, is subjected to treatment with a Vilsmeier reagent (phosphorus oxychloride together with dimethylformamide), followed by hydrolysis. The substituted-pyrano[3.2-c] [l,2]benzothiazine 6,6- dioxides of formula I prepared by the process of this invention have anti-secretory activity and are useful in the treatment of hyperacidity; certain of these compounds demonstrates anti-allergy activity.

4 Claims, No Drawings PROCESS FOR THE PREPARATION OF SUBSTITUTED PYRANO (3,2-C) (1,2)BENZOTHIAZINE 6,6-DIOXIDES SUMMARY OF THE INVENTION This invention relates to a novel process for preparing compounds of the formula I:

wherein R represents hydrogen and lower alkyl; R represents lower alkyl and formyl which comprises react ing a starting material of the formula II or III:

O on @w so NR SO N-R wherein R represents hydrogen and lower alkyl, with a boron trifluoride compound (preferably boron trifluoride etherate) and, in the case of starting material I], with an acid anhydride of the formula IV:

(R'CH CO) O wherein R represents hydrogen or lower alkyl, to obtain a boron complex intermediate having the formula V.

BF 0/ 2\O+ DETAILED DESCRIPTION OF THE INVENTION The novel reaction of the instant invention and the novel intermediates and final products produced thereby are represented. Starting material ll (2- substituted-2Hl ,2-benzothiazin-4(3H)-one 1,1- dioxide) is reacted with an acid anhydride IV and a boron trifluoride compound in the first step of the process of this invention; alternately, starting material 111 (3-acetyl-2-substituted-2H-l ,2-benzothiazin- 4(3H)-one 1,1-dioxide) may be reacted with the boron trifluoride compound alone, the acid anhydride IV being unnecessary when starting material III is used. Using either starting material 11 or III in first step of the process of this invention yields the novel, substituted boron complex intermediates V which are reacted with a Vilsmeier reagent, followed by hydrolysis, to obtain the final compounds having formula I.

The Vilsmeier reagent used is phosphorus oxychloride (POCI with dimethylformamide (DMF). The substituents obtained on final compound I depend on the boron intermediate V used. For example, if R in the boron intermediate V is methyl (i.e., the substituent in the 4-position is methyl) and DMF is used, a final compound I is obtained wherein R is 3-formyl, as in Examples VII to X.

However, when R in the boron intermediate V is ethyl and DMF is used, a final compound I is obtained wherein R is 3-methyl, as in Example XI.

Another unusual result occurs during the process of this invention when 3-acetyl-2H-1,2-benzothiazin- 4(3H)-one, 1,ldioxide is used as the starting material III in the process of this invention: an acetyl group attaches to the nitrogen atom of the boron intermediate complex, i.e., 5-acetyl-2,2-difluoro-4-methyl-2H-1,3,2- dioxaborino[5,4-c]1,2-benzothiazine 6,6-dioxide is formed (see Example IV). During the second step of the reaction, this 5-acetyl group is removed and the nitrogen atom in the final compound is unsubstituted.

The starting materials 11 and 111 used in the process of this invention are prepared by known methods or obvious adaptations thereof, as described in Zinnes, H. et. al., 1,2-Benzothiazines. II. The Preparation and Sodium Borohydride Reduction of 3-Acyl-2H-l ,Z-benzothiazin-4(3H)-one, l,1-Dioxides, J. Org. Chem 30: 2241-2246 (1965) and in Zinnes, H. et al., 1,2- Benzothiazines. III. The Preparation of 2H-l,2-Benzothiazin-4(3H)-one 1,1-Dioxide by the Acid-Catalyzed Deacetylation of B-Diketone, J. Org. Chem. 31: 162-165 (1966). g

The boron trifluoride compound used in the process of this invention is preferably boron trifluoride etherate.

The intermediate boron complex V prepared in the process of this invention is novel and useful in the preparation of final compounds I which are, in turn, pharmacologically active.

Novel intermediates having formula V above form an especially preferred group when R represents methyl, ethyl, butyl or acetyl; and R represents methyl or ethyl.

Final compounds prepared according to the process of this invention, as well as certain other closely related compounds having the formula VI below:

. VI O N-R S wherein R represents hydrogen and lower alkyl; and R represents lower alkyl, formyl and hydroxymethyl and their corresponding aldehyde thiosemicarbazone derivatives, are more fully described in co-pending application Ser. No. 365,399, filed May 29, 1973. These compounds having formula VI exhibit anti-secretory effects and can be used in relieving gastric hyperacidity. Compounds having formula VI, when administered to mammals, such as rats and guinea pigs, in a suitable vehicle as described below, inhibit the gastric secretion of hydrochloric acid; acidity in the stomach is thus reduced. Pharmaceutical compositions containing compounds of formula VI are indicated in the management of gastric hyperacidity and in the treatment of peptic ulcer resulting from such hyperacidity.

Compounds of formula VI, when tested according to the procedure of H. Shay, Gastroenterology 5: p. 43 (1945-) are effective in reducing gastric acidity in the pylorus ligated rat when administered intraperitoneally at a dosage of 5 to mg/kg of body weight. At a dosage of 5 to 40 mg/kg of body weight, administered intraduodenally, the same compounds are effective in reducing gastric acidity when subjected to this last mentioned test. Thus, the effective dose range for treatment of gastric hyperacidity is from 5 to 40 mg/kg of body weight of the mammal being treated, administered parenterally. Pharmaceutical compositions containing compounds having formula V] may be administered in an aqueous gum tragacanth suspension as an intramuscular injection. The dosage regimen of from 5 to 40 mg/kg of body weight may be varied depending upon the severity of the condition and the weight, age and sex of the mammal being treated.

Compounds described in aforementioned co-pending application Ser. No. 365,399, filed May 29, 19 73, having formula Vll below:

VII

wherein R represents lower alkyl; and R represents formyl and hydroxymethyl have also been found to be useful in the treatment of allergic conditions. Thus, compounds of formula Vll reduce responses to antigen challenge by inhibiting antibody and antigen reactions in mammals when tested in accordance with the procedure of 1. Meta, Life Sciences 2: No. 7, p 465-474 (1963) and Ovary, Z. et al, Proc. Soc. Exptl. Biol. Med. 81: p 584-586 (1952). The compounds may be administered to mammals such as rats or guinea pigs. parenterally or orally, at dosages of approximately 100 mg/kg of body weight.

Compounds of formula Vll may be administered in a parenterally acceptable vehicle such as a gum tragacanth suspension or they may be combined with pharmaceutical diluents such as lactose, cornstarch and the like and formulated into tablet or capsule dosage forms.

Pharmaceutical compositions containing compounds of formula Vll are useful in'the'managementof allergic conditions such as bronchial asthma. To treat bronchial asthma, a dose of lOO mg/kg of body weight administered orally or parenterally is suggested. This dosage may be varied depending on the condition of the patient.

ln formulas l Vll above, the terms used to describe substituents are more fully defined as follows: lower alkyl is meant to include lower aliphatic hydrocarbons having one to six (preferably one to four) carbon atoms in the carbon chain, such as methyl, ethyl, propyl, isopropyl, butyl, and isobutyl. The acyl in the term lower acyl is meant to include lower alkyl carboxylic acid wherein the lower alkyl moiety has the above described meaning.

- In order to further illustrate the practice of this invention, the following examples are included:

EXAMPLE I Preparation of 2,2-difluoro-4,S-dimethyl-2H-l ,3,2-dioxaborino [5,4-'c]-l ,2-benzothiazine 6,6-Dioxide (Procedure A) Seventy-one grams (0.5 mole) of boron trifluoride etherate is added to 42.3 g. (0.2 mole) of 2-methyl-2l-ll,2-benzothiazin-4(3H)-one, l,l-dioxide* in 102 g. (1.0 mole) of acetic anhydride. The mixture is heated for 4 hrs. on a steam bath and then refluxed for 1 hr. The mixture is cooled, diluted with 250 ml. of ether, stirred and filtered to yield lt. brown solid complex; mp l63-l 72C. [Dry weight 58.7 g. (97%)]. The analytical sample is obtained by recrystallization from ethyl acetate: Skellysolve C; mp 2132l4C.

*Prepared by the method of H. Zinnes, R. A. Comes and .I. Shavel, Jr.,

J. Org. Chem., 31, 162 (1966).

Anal. Calcd for C H BF NO S: C, 43.88; H, 3.35; H, 4.65; S, 10.65. Found: C, 44.16; H, 3.43; N, 4.55; 5, 10.75.

EXAMPLE ll Preparation of 4-ethy1-2,2-dii'luoro-5methyl 2H-1,3,2-dioxaborino [5 ,4-c] 1 ,2-benzothiazine 6,6-Dioxide (Procedure A) Starting with 2-methyl-2H-1,Z-benzothiazin- 4(3H)-one l,1-dioxide* and following the procedure A of Example 1, but substituting propionic anhydride for acetic anhydride 4-ethyl 2,2-difluoro-5-methyl-2H- 1,3 ,2-dioxaborino[5,4-c] 1 ,2-benzothiazine 6,6-dioxide is obtained having an mp of 134-136C.

Prepared by the method of H. Zinnes. R. A. Comes and J. Shave], Jr.. J. Org. Chem.. 31. 162 (1966).

Anal. Calcd: C H BF NO S: C, 45.74; H, 3.84; N, 4.45; F, 12.06. Found: C, 45.62; H, 3.94; N, 4.19; F, 12.17.

EXAMPLE [11 Preparation of 2,2-difluoro-4,5-dimethy1-2H-1,3 ,2-dioxaborino [5,4-c1-1,2-benzothiazine 6,6-Dioxide (Procedure B) identical to the material prepared by Example 1. *Prepared by method of H. Zinnes, R. A. Comes, F. R. Zuleski, A. N. Caro and J. Shavel, .Ir.. J. Org. Chem., 30, 2241 (1965).

EXAMPLE 1V Preparation of 5-acetyl-2.2-difluoro-4-methyl-2H-1,3 ,2dioxaborino [5,4-c] 1,2-benzothiazine 6,6-Dioxide (Procedure B) Starting with 4(3H)-one 1,1-dioxide* and following procedure B of Example 111, 5-acetyl-2,2-difluoro-4-methyl-2H-l,3,2-

6S 3-acetyl-2H- 1 ,Z-benzothiazm- 6 dioxaborino[5,4-c]1,2-benzothiazine 6,6-Dioxide is obtained having an mp of 195197C.

*Prepared by the method of H. Zinnes, R. A. Comes and .l. Shavel, Jr.. J. Org. Chem., 31: 162 (1966) J Anal. Calcd: C H BF NO S: C, 43.80; H, 3.06; S, 9.74. Found: C, 44.13; H, 3.08; S, 9.85.

EXAMPLE V Preparation of 5-ethy1-2,2-difluoro-4-methyl-2H-1,3 ,2-dioxaborino [5,4-c]1,2-benz0thiazine 6,6-Dioxide (Procedure B) Starting with 3-acetyl-2-ethyl-2H-l,2-benzothiazin- 4(3H)-one 1,1-dioxide and following the procedure B of Example 111, 5-ethyl-2,2-difluoro-4-methyl-2H- 1,3,- 2-dioxaborino[5,4-c]1,2-benzothiazine 6,6-Dioxide is obtained having an mp of 167l69C.

Anal. Calcd: C, H, BF NO S: C, 45.74; H, 3.84; S, 10.18. Found: .C, 45.50; H, 3.87; S, 10.39.

EXAMPLE V1 Preparation of 5-n-buty1-4-methyl-2H-1 ,3,2-dioxaborino[5 ,4-c]1,2 benzothiazine 6,6-Dioxide (Procedure B) Starting with 3-acety1-2-n-buty1-2H-1,2-benzothiazin-4(3H)-one 1,1-dioxide and following the procedure B of Example Ill, 5-n-butyl-4-methyl-2H-1,3,2- dioxaborino[5,4-c]1,Z-benzothiazine 6,6-dioxide is obtained having an mp of -102C.

Anal. Calcd: C,;,H BF NO S: C, 49.00; H, 4.73; S, 9.34. Found: C, 49.16; H, 4.73; 8,941.

EXAMPLE V11 SOgI-CH;

Preparation of 5-methyl-4-oxo-4H,5H-pyrano[ 3,2-c][ 1,2]benzothiazine- 3-carboxaldehyde 6,6-Dioxide (Procedure C) A solution of reagent is prepared by the slow addition of 153 g. (1.0 mole) of phosphorus oxychlorideto ice cold DMF (365 g., moles). The temperature is maintained below C by use of a Cooling bath. After stirring for an additional half-hour, 150 g. (0.5 mole) of 2,2-difluoro-4,5-dimethyl-2H-1,3 ,2-dioxaborino[ 5 ,4- c]-1,2-benzothiazine 6,6-dioxide is added and the reaction mixture is stirred for minutes. The mixture is heated for 2 hours on a steam bath and poured over 2,500 ml. ice water. After standing overnight, the mixture is filtered to yield 1t. brown solid product; mp 246-254C. Dry weight equals 131.6 g. (90% yield). The analytical material, recrystallized from DMF, melted at 258259C,(dec).

Anal. Calcd for C H NO S: C, 53.61; H, 3.11; N, 4.81; S, 11.01. Found: C, 53.33; H, 3.09; N, 4.90; S, 10.83.

EXAMPLE Vlll Preparation of 5-methyl-4-oxo4H ,5H-pyrano[ 3,2-c]-1 ,2- benzothiazine-3-carboxaldehyde 3-thiosernicarbazone 6,6-dioxide.

. hemihydrate The product of Example VII is reacted with thiosemicarbaside in dioxane to obtain 5-methyl-4-0xo- 4H,5H-pyrano[3,2-c]-1,2-benzothiazine-3- carboxaldehyde 3-thiosemicarbazone 6,6-dioxide hemihydrate having an mp of 227229C (dec).

Anal. Calcd: C H N S O H O: C, 45.03; H, 3.51; N, 15.00; S, 17.17. Found: C, 45.13; H, 3.49; N, 14.91; S, 16.85.

EXAMPLE IX Preparation of 5-ethyl-4-oxo-4H,SH-pyrano[3,2- c][ 1 ,2]benzothiazine-3-carboxaldehyde 6,6-dioxide (Procedure C) Starting with 5-ethyl-2,2-difluoro-4-methyl-2H- 1,3,2-dioxaborino[5,4-c]1,2-benzothiazine 6,6-dioxide from Example V and following procedure C of Example V11, 5 -ethyl-4-oxo-4H ,5 H-pyrano[ 3 ,2- c][l,2]benzothiazine-3-carboxaldehyde 6,6-dioxide is obtained having an mp of 160162C.

Anal. Calcd: C H NO S: C, 55.08; H, 3.63; N,-4.59. Found: C, 54.96; H, 3.56; N, 4.11.

EXAMPLE X Preparation of 5-n-buty1-4-oxo-4H ,5H-pyrano[ 3 ,2- c 1,2]benzothiazine-3-carboxaldehyde 6,6-dioxide (Procedure C) Starting with 5-n-butyl-4-methyl-2l-l-1,3 ,2- dioxaborino[5,4-c] 1,2-benzothiazine 6,6-dioxide from Example VI, and following procedure C of Example VII 5-n-butyl-4-oxo-4H,5H-pyrano[3,2-c] [1,2]benzothiazine-3-carboxaldehyde 6,6-dioxide is obtained, having an mp of l08-110C.

Anal. Calcd.: C H NO S: C, 57.65; H, 4.54; N, 4.20. Found: C, 57.70; H, 4.58; N, 4.24.

EXAMPLE Xl Preparation of 3,5-Dimethylpyrano[3 ,2-c][1,2]benzothiazin- 4(5H)-one 6,6-di0xide (Procedure C) Starting with 4-ethyl-2,2-difluoro-5-methyl-2H- 1 ,3 ,2-dioxaborino[5,4 c]-1,2-benzothiazine 6,6- dioxide from Example I1 and using procedure C of Example VII, the subject compound is obtained as an almost colorless crystalline product; mp 2l42l6C (from chloroform: Skellysolve C).

Anal. Calcd: C H NO S: C, 56.31; H, 4.00; N, 5.05. Found: C, 56.20; H, 3.97; N, 5.07.

I claim: 1. A process for preparing a compound of the formula l:

whcrern R represents hydrogen and lower alkyl; R represents lower alkyl and formyl which comprises reacting a starting material of the formula ll; 5

wherein R represents hydrogen and lower alkyl, with a boron trifluoride compound selected from the group consisting of boron trifluoride and boron trifluoride etherate, and with an acid anhydride of the formula IV:

wherein R represents hydrogen or lower alkyl to obtain a boron complex intermediate having the formula V:

wherein R represents hydrogen and lower alkyl; R represents lower alkyl and formyl which comprises reacting a starting material of the formula Ill:

III

wherein R represents hydrogen and lower alkyl, with a boron trifluoride compound selected from the group consisting of boron trifluoride and boron trifluoride etherate, to obtain a boron complex intermediate having the formula V:

wherein R represents hydrogen, lower alkyl and lower alkanoyl and R represents lower alkyl, and reacting intermediate V with phosphorus oxychloride together with dimethylformamide, followed by hydrolysis.

4. A process according to claim 3 wherein the boron trifluoride compound is boron trifluoride etherate. 

1. A PROCESS FOR PREPARING A COMPOUND OF THE FORMULA I:
 2. A process according to claim 1 wherein the boron trifluoride compound is boron trifluoride etherate.
 3. A process for preparing a compound of the formula I:
 4. A process according to claim 3 wherein the boron trifluoride compound is boron trifluoride etherate. 